I'm not a professional breeder, but the way I understand it you'd use the Marans Roo and the F1 to get a F2. Logically thinking a F1 roo and F1 hen would be another F1, but again I'm not a professional breeder and I'm just having fun with chickens. One may come along and say different.Do I breed my F1 roo to my dark layer or F1 hens to dark layer to get F2?